The sizing, shaping, and surface finishing of metals for complex parts such as turbine blades, impellers, vessels, and the like has often proven to be a challenge. One commonly used method for shaping and finishing metals and metal alloys is etching. However, most commonly used etching solutions employ materials such as hydrofluoric acid that are hazardous to handle and difficult and expensive to dispose of. An alternative to etching is electropolishing, but there is a need for electropolishing materials and methods that achieve high surface smoothness, and are less expensive, less corrosive, and more environmentally friendly than current etching materials and methods.
An electropolishing solution effective for surface finishing of metals comprises about 75 to about 99 weight percent of an alkylene glycol; and about 1 to about 25 weight percent of a chloride salt selected from the group consisting of alkali metal chlorides, alkaline earth metal chlorides, and combinations thereof.
Other embodiments, including an electropolishing method and a method of recovering a spent electropolishing solution, are described in detail below.